The goal of this project is to develop and optimize procedures for fabricating intracortical microelectrodes that provide a stable interface with neural tissue. The utility of this goal is to be able to utilize neuronal activities as a source of control signals for a neuroprosthesis. Because a number of mechanisms can cause changes in the electrode-tissue interface, it is essential to develop techniques that can quantify and monitor these changes and to refine the design of microelectrodes. It is also important to improve implantation techniques to make the electrode-tissue interface more stable and provide a higher yield of resolvable neural units. The project has two objectives. The first is to develop/refine a computerized system that sorts spikes obtained in a recording session to single neural units, assigns the neural units obtained across successive sessions to appropriate neurons, and quantifies the stability of the electrode-tissue interface. The second is to use these methods to optimize the design of microelectrodes and/or microelectrode arrays, and to refine and develop appropriate implantation techniques for this application. The primary goal of this project is to refine a existing microelectrode technology in a cat model to the point where it can be tested in old world monkeys, and thereby allow the development of the neuroprosthesis concept to the next level.